1. Field of the Invention
This invention relates to liquid spray nozzles. More particularly, it relates to nozzles in which the liquid discharge is randomly directionally unstable over a wide range of applied liquid pressures.
2. Review of the Prior Art and General Background
My prior U.S. Pat. No. 3,684,176 describes a liquid discharge nozzle which is arranged to produce a discharge which pulsates randomly in intensity and in which the principal discharge trajectory oscillates randomly within a basic conical limiting envelope defined by the nozzle structure. This then-novel discharge characteristic, as set forth in the patent, is produced when the nozzle has an elongate inner chamber, a restricted inlet to the chamber at one end thereof, and a single outlet duct from the chamber having an area much less than the mean transverse area of the chamber but greater than the inlet area and also a conically flared outlet end. In such a nozzle, the inlet to the chamber is formed through a plug-like septum at the inlet end of the chamber. Thus, according to my prior patent, the desired discharge characteristic described therein required the use of a nozzle having an inlet to and an outlet duct from the chamber, the inlet and the outlet each having an area less than cross-sectional area of the chamber with the outlet duct being of greater area than the inlet; the prior nozzle also required a conical flare on the outer end of the outlet duct.
Nozzle structures in accord with the teachings and descriptions of my prior U.S. Pat. No. 3,684,176 function to produce a randomly directionally unstable discharge characteristic only when the liquid (typically water) applied to the nozzle is at relatively high pressure of about 25 pounds per square inch gage pressure or more; these nozzles produce this discharge characteristic for all applied water pressures greater than the threshold pressure associated with the initial manifestation of the unique discharge effect.
Shortly following the filing of the patent application which resulted in U.S. Pat. No. 3,684,176, and before the issuance of the patent on that application, I undertook a research and development program in an effort to produce a nozzle structure which would produce this unique discharge characteristic when the applied water pressure was relatively low, say on the order of 5 psig or less, and which would maintain the discharge characteristic over a wide range of higher applied water pressures. This research and development program extended for approximately five years. I commenced this research and development program because I discerned a need for nozzles of the nature which the program sought to produce. Nozzles of such nature can be used in shower heads as well as in liquid discharge devices for industrial purposes.
In the course of this research and development program, I found that I could make most any nozzle structure, defined in accordance with the teachings of my prior patent, function to produce the randomly directionally unstable discharge characteristic if the nozzle structure included an inlet choke (i.e., the inlet opening to the chamber was defined through a septum at the inlet end of the chamber) and if the inlet opening had an effective water flow area less than the effective water flow area of the outlet duct from the chamber. I was unable, until making the discovery which is an aspect of the present invention, to produce a nozzle structure in accord with my prior patent which operated reliably to produce the desired discharge characteristic when operated over a wide range of applied water pressures beginning at about 5 psig or less. The problem which I encountered with nozzles structured according to the descriptions of my prior patent was one of pressure loss and inefficiency due to the effects of the restricted inlet to the chamber within the nozzle. In an attempt to reduce pressure loss through the nozzle and to improve the liquid discharging efficiency of the nozzle structure, the inlet opening of the prior nozzle was made larger than the area of the outlet duct, but I found that this structural variation caused a loss of any ability to predictably produce the desired discharge characteristic over the desired wide range of water pressure. In other words, as the inlet opening to the chamber was enlarged to be equal to or greater than the area of the outlet duct from the chamber to the exterior of the nozzle, the ability to produce a reliable operating nozzle having a reliably predictable discharge oscillation threshold pressure became a random occurrence.
I have now discovered that the randomly directionally unstable discharge characteristics of the type produced by nozzles described in my prior patent 3,684,176 can be obtained predictably in nozzle structures which have no flow-restricting plug-like septum across the interior of the nozzle body and through which the inlet is defined to the chamber from which the outlet duct communicates. In the "plugless" or "unchoked" nozzles to which this patent application is addressed, the desired randomly directionally unstable discharge characteristic is accomplished in a predictable manner over a wide range of pressures, beginning at low pressures on the order of 5 psig or less, by the proportioning and geometry of the outlet duct from the nozzle. One aspect of the present invention is the recognition that the relationships and structural features described in U.S. Pat. No. 3,684,176 are, in effect, a special case, which in some respects is an optimum case, of broader relationships which can be used to produce the same result. This invention removes limitations from the technology and art pertinent to nozzles of the type described in my prior patent, and thereby advances the pertinent technology and art.
I have also discovered that nozzles of the type described in my prior patent are not readily scalable from one size to another, particularly into small size nozzles. It is believed that this difficulty in downward scaling of nozzles according to my prior patent is due, at least in part, to the increasing significance and effect of liquid viscosity as the size of the nozzle is reduced.
The prior art specifically considered in the preparation of this patent application includes the following U.S. Pat Nos. 487,628; 604,873; 1,104,965; 1,762,313; 1,940,171; 1,983,634; 2,106,427; 2,175,160; 2,295,228; 2,550,573; 2,573,982; 2,735,719; 2,978,189; 3,003,548; 3,045,932; 3,054,563; 3,178,121; 3,198,442; 3,230,924; 3,240,253; 3,263,934; 3,300,142; 3,314,612; 3,326,473; 3,337,135; 3,423,026; 3,469,642; 3,490,696; 3,628,726; 3,643,866; 3,666,183; 3,675,855; 3,684,176; 3,687,369; 3,747,859; 3,750,961; 3,756,575; 3,774,846; 3,810,583; 3,823,408; and 3,884,417.